Farmer‘s daughter. Her mother died when Margaret was seven years old, and her stepmother considered the girl a nuisance. Margaret eloped with a young nobleman from Montepulciano, bore him a son, and lived as his mistress for nine years. In 1274 he was murdered by brigands, and his body dumped in a shallow grave.

Margaret saw the incident as a sign from God. She publicly confessed to the affair, and tried to return to her father‘s house; he would not accept her. She and her son took shelter with the Friars Minor at Cortona. Still young and attractive, Margaret sometimes had trouble resisting temptation, but each incident was followed by periods of deep self-loathing. To make herself unappealing to local young men, she once tried to mutilate herself, but was stopped by a Friar named Giunta.

She earned her keep by tending to sick women. She later began caring for the sick poor, living on alms, asking nothing for her services. She became a Franciscan tertiary in 1277. Margaret developed an deep and intense prayer life, and was given to ecstacies during which she received messages from heaven.

In 1286 Margaret received a charter to work with the sick poor. She gathered others of like mind, and formed them into a community of tertiaries. They were later given the status of a congregation, and called the Poverelle (Poor Ones). With them she founded a hospital at Cortona. Margaret preached against vice of all sorts to any who would listen. She developed a great devotion to the Eucharist and Passion, and prophesied the date of her own death.

Though she worked for those in need, and though the poor sought her help and advice, the calumny of her earlier life followed her the rest of her days, and she was forever the target of local gossips.